Determination of the optimal parameters maximizing muscle activity of the lower limbs during vertical synchronous whole-body vibration.

PURPOSE: To describe the most effective parameters maximizing muscle activity during whole-body vibration (WBV) exercises on a vertically vibrating (VV) platform. METHODS: The influence of (1) WBV vs. no vibration, (2) vibration frequency (25, 30, 35, 40 Hz), (3) platform peak-to-peak displacement (1.2, 2 mm), and (4) additional loading (no load, 17, 33 kg) on surface electromyographic (sEMG) activity of five lower limb muscles was investigated in eighteen participants. RESULTS: (1) Comparing WBV to no vibration, sEMGRMS of the calf muscles was significantly higher with an additional load of 33 kg independently of the displacement and the frequency (P < 0.05). During WBV, (2) muscle activity at 40 Hz WBV was significantly higher than at 25 Hz for the gastrocnemius lateralis (GL) for all loads, and for the vastii medialis and lateralis using the 33 kg load (P < 0.05); (3) sEMGRMS of all lower limb muscles was significantly increased with the 2 mm compared to the 1.2 mm peak-to-peak displacement (P < 0.05); (4) an effect of additional load was found in the GL, with significantly higher neuromuscular activation for the 33 kg load than no load (P < 0.05). CONCLUSIONS: On a VV platform, we recommend the use of a high platform displacement in combination with a high vibration frequency to provoke the highest muscle activity enhancement. Without maxing out the acceleration stimuli, calf muscles' sEMG can be enhanced with an additional load of 33 kg which corresponded to 50 % of the body mass.